Conventionally, electrophotographic image-forming apparatuses such as LED printers are well-known in the art. The image-forming apparatuses may use developing cartridges. Such a developing cartridge may include a developing roller configured to supply toner. Such conventional image-forming apparatuses are disclosed in prior arts. For example, a prior art discloses an image-forming apparatus including a drawer unit. The drawer unit includes a photosensitive drum. A developing cartridge is configured to be attached to the drawer unit. When the developing cartridge is attached to the drawer unit, the photosensitive drum and the developing roller contact each other.
Another prior art discloses a developing cartridge that is configured to be attached to a drum cartridge. The drum cartridge includes a photosensitive drum. When the developing cartridge is attached to the drum cartridge, the photosensitive drum and the developing roller contact each other. The drum cartridge having the developing cartridge attached thereto is attached to an image-forming apparatus.